What is a forced ventilation system?
In heating, ventilation, and air conditioning (HVAC) systems, the distribution chamber is a chamber that provides the distribution of air processed in the unit. It is connected to the air handling unit and can perform the function of supplying air to be processed or receiving air that has already been processed. In office buildings, where the space above the suspended ceiling is used for air circulation, this space is also considered a return air chamber.
It is important to note that in various industries and types of products, such as communication cables, similar terms are presented, but the definition of "distribution chamber" may differ.
Marking of the distribution chamber
In the context of HVAC, "marking of the distribution chamber" means the permissible locations for installing products that contain the HVAC system. Products that can be safely installed in the conditioned air stream according to UL company standards are marked with this marking. This marking indicates that the product is suitable for installation anywhere in the conditioned air stream.
UL (Underwriters Laboratories) Requirements
UL's safety focus regarding marked drives is concentrated on preventing the spread of fire and smoke formation in the HVAC system. When selecting building materials correctly, such drives should not contribute to the ignition, excessive smoke formation, or pollutants when exposed to fire and high temperatures.
Current UL standards include UL 508C and UL 1995, which establish criteria and testing methods for awarding marking of the distribution chamber. UL uses the term "pollution degree," where pollution degree 3 is considered the most complex. Yaskawa drives are designed for operation in distribution chambers with pollution degrees 1 and 2, excluding situations with moisture, where surfaces may become conductive due to humidity and contamination.
What do I need to know?
- Many Yaskawa drives have been assigned distribution chamber marking.
- Yaskawa drives meet technical requirements for pollution degrees 1 and 2 (regarding dry, non-conductive surfaces).
- Yaskawa drives do not meet technical requirements for pollution degree 3 (surfaces that may be wet and conductive).
What should I check before installing a Yaskawa drive in a distribution chamber?
- Ensure that the drive has distribution chamber marking.
- Make sure that the pollution level for the drive (2) meets or exceeds the pollution level for the selected area of the distribution chamber.
- Ensure that the Yaskawa drive has a NEMA type 1 or higher enclosure protection class.
Where should drives be located in the distribution chamber?
- Place the drive in the conditioned air stream to ensure its protection and to facilitate maintenance.
- Do not place the drive in a location where it will be subjected to unfiltered return air at high velocity, which can lead to contamination.
- Do not install the drive in areas where the supply air is directed downward from cooling coils, where relative humidity may exceed 95%, which can lead to condensation.